1. Field of the Invention
The present invention relates to a dental glass ionomer cement composition having excellent adhesion strength to a metallic prosthesis.
2. Description of the Conventional Art
In dental treatments, cement materials such as zinc phosphate cement, glass ionomer cement, resin cement and the like have been used as a material for bonding a dental prosthesis such as a crown, an inlay, a bridge or the like to a tooth lost part damaged due to a dental caries, an accident or the like. In the basic concept for restoring a tooth lost part, a material having a suitable strength is used in a space between the tooth lost part and the prosthesis so as to bond them.
Among these materials for bonding the prosthesis, dental glass ionomer cement mainly including polycarboxylic acid, a fluoroaluminosilicate glass powder and water is cured by acid-base reaction of polycarboxylic acid and fluoroaluminosilicate glass powders under the existence of water. It has been known that the dental glass ionomer cement releases fluoride effective for strengthening a tooth. In addition, the dental glass ionomer cement has been widely used as an excellent dental material having high hydrophilicity and excellent adhesiveness to the tooth. However, since the dental glass ionomer cement has low chemical interaction of polycarboxylic acid to the metallic prosthesis, it has been difficult to acquire sufficient adhesiveness.
A resin-reinforced glass ionomer cement acquired by adding a (meth)acrylate monomer to the dental glass ionomer cement as a resin component has been used. The resin-reinforced glass ionomer cement can increase a bending strength of a cured body by visco-tenacity of the polymerized resin component, so that frictional force increases between the cement and the prosthesis. Thus, mechanical retentivity between the tooth and the prosthesis is improved. However, since the resin component hardly has interaction with the metallic prosthesis, there is no effect to improve chemical adhesion strength.
Accordingly, in order to acquire adhesiveness to the tooth, adhesive resin-reinforced glass ionomer cement blended with a polymerizable monomer having an acid group has been discussed (e.g., refer to Japanese Patent Application Laid-Open No. 2003-012433). The patent application No. 2003-012433 discusses that, in the polymerizable monomer having an acid group, a polymerizable monomer having a thiophosphoric acid group is preferably used because of having excellent adhesiveness to the prosthesis. Since the polymerizable monomer having a thiophosphoric acid group includes, in its structure, a sulfur atom with high compatibility to metal, the adhesiveness to the metallic prosthesis is improved. However, polymerizability is lower than the other polymerizable monomers, and there is a problem that the adhesion strength may decrease when polymerization is insufficient. When the amount of a polymerization initiator increases so as to secure the polymerizability, there is a problem that stability of a product decreases.
Furthermore, when the metallic prosthesis is bonded using the resin cement, various kinds of surface treatment agents (primers) are used to increase the adhesiveness. Specifically, in a treatment of a metallic prosthesis mainly including gold, platinum, palladium, silver and the like, surface treatment agents including a polymerizable monomer having a functional group containing a sulfur atom (a primer for metal) have been used (e.g., refer to Japanese Patent Application Laid-Open Nos. 2002-265312, 2008-056649 and 2009-067746). These surface treatment agents have high compatibility to metal, which is induced by a sulfur atom contained in a specific functional group in the surface agents. In addition, a polymerization group in the surface treatment agent is copolymerized with a matrix of the resin cement. Accordingly, the surface treatment agents can exercise effect to increase the adhesiveness of a resin component with metal. However, comparing with the resin cement which needs a surface treatment, the dental glass ionomer cement has an advantage which can bond to the tooth without performing the surface treatment. Thus, when the dental glass ionomer cement is used, it is not desirable with the latest tendency to take much time and effort to use the metallic primer on the surface of the metallic prosthesis.